[pull] main from django:main

django/forms/fields.py

@@ -40,6 +40,7 @@
 )
 from django.utils import formats
 from django.utils.choices import normalize_choices
+from django.utils.datastructures import OrderedSet
 from django.utils.dateparse import parse_datetime, parse_duration
 from django.utils.duration import duration_string
 from django.utils.ipv6 import MAX_IPV6_ADDRESS_LENGTH, clean_ipv6_address
@@ -965,8 +966,8 @@ def validate(self, value):
         if self.required and not value:
             raise ValidationError(self.error_messages["required"], code="required")
         # Validate that each value in the value list is in self.choices.
-        # Use set() to avoid redundant validation.
-        for val in set(value):
+        # Avoid redundant validation, and keep elements ordered.
+        for val in OrderedSet(value):
             if not self.valid_value(val):
                 raise ValidationError(
                     self.error_messages["invalid_choice"],

tests/forms_tests/field_tests/test_multiplechoicefield.py

@@ -91,5 +91,5 @@ def test_validate_duplicated_values(self):
 
     def test_validate_duplicated_invalid_values(self):
         f = MultipleChoiceField(choices=[("1", "one"), ("2", "Two")])
-        with self.assertRaises(ValidationError):
-            f.validate(["1", "1", "invalid", "invalid"])
+        with self.assertRaisesMessage(ValidationError, "invalid-one"):
+            f.validate(["invalid-one", "invalid-one", "invalid-two"])